An electric drive can be provided as the only drive for the motor vehicle or it can be provided in addition to an internal combustion engine. In the latter case, the electric drive and the internal combustion engine can drive the vehicle individually or jointly by being superimposed on one another. Such drive concepts are also referred to as “hybrid drives”.
Usually, an electric drive comprises an electric motor and a following reduction drive which translates a rotational movement from a high speed into a low speed. From the reduction drive the torque is transferred to the driveline of the motor vehicle. For this purpose, a differential drive following the reduction drive in the torque flow divides the introduced torque to two output shafts for driving the vehicle wheels. The two output shafts of the differential drive have a balancing effect relative to one another, i.e., if one of the two output shafts rotates faster, the other output shaft moves correspondingly slower, and vice versa.
From WO 2012/087700 A1 an electric drive module is known having an electric motor, a planetary drive, a synchronising unit, a reduction drive and a differential assembly. The synchronising unit is operated by an actuator which comprises a rotatingly drivable spindle drive for axially moving a shift fork which cooperates with a sliding sleeve of the synchronising unit.
From WO 2007/110131 A1 an actuating assembly for a shiftable clutch of a multi-step transmission is known. The actuating assembly comprises an electric machine, a rotatable shaft drivable thereby, and an operating member arranged on the rotatable shaft. The operating member is connected to a rotor of the electric machine via a rotation translation convertor.
DE 10 2006 011 207 A1 proposes a sensor assembly for recording a position of a movable element. The sensor assembly comprises a magnetic field sensor which, in different positions of the movable element, records different magnetic field strengths.
From WO 2005/098269 A2 an automatic multi-step transmission is known with several gear stages which can be engaged and disengaged by respective clutches. The clutches are provided in the form of synchronous clutches which are actuated by an axially displaceable switching sleeve. The switching sleeve is operated by a controllable actuator.
DE 10 2005 022 926 B3 proposes a process for optimising the switching sequence of a multi-step transmission of a motor vehicle. The multi-step transmission comprises a plurality of gear stages which can be engaged by respective clutches. The switching sequence provides for a tolerance- and/or wear-dependant parameter to be recorded and for setting a nominal path value of the switching member of the clutch.
Electric drives with multi-step transmissions with switching clutches require a major constructional effort for the clutches and actuators. A multi-step transmission with a synchronising unit requires high switching forces, thus involving high demands to be met by the actuator. Furthermore, production tolerances and the amount of wear occurring during the service life of same can lead to switching inaccuracies.